The invention relates to a method and apparatus for coupling laser radiation to a cataract lens in the eye to ablate the same.
Every eye is divided into an anterior and posterior chamber separated by a normally transparent lens which focuses light onto the retina at the back of the posterior chamber. When the lens becomes cloudy for any of a variety of reasons sight is impaired and the cloudy lens must be removed. Following removal of the lens, an intraocular lens (IOL) implant can be placed in the posterior chamber or thick glasses or contact lenses used to focus the light.
A number of techniques are now in use for this common surgical procedure. An incision can be made in the eye and a sharp instrument inserted to cut and then aspirate by vacuum the cloudy cataract tissue. More recently, a small incision-typically 3 mm-can be made in the eye surface and an ultrasonic probe inserted to a position adjacent to the lens. The ultrasonic energy then disintegrates the lens material which can likewise be removed by aspiration.
Laser radiation is now used widely in various surgical techniques particularly those involving the eye. For example, the patent to Krasnov, 3,971,382, describes a technique in which laser radiation is focused onto the anterior capsule of the lens to form a hole through which the cataract substance can be drawn from the lens capsule.
Optical fibers are also commonly used for medical and other applications to transmit coherent radiation from a laser to some location in the body where material is to be coagulated or disintegrated. U.S. patent application Ser. No. 702,569, filed Feb. 19, 1985, describes a micro instrument with an optical fiber. The optical fiber can be inserted into the eye for the removal of abnormal tissue such as tumors. Radiation with a wavelength between 200 and 400 nm is said to be appropriate.
The present invention relates to a method and apparatus in which coherent radiation is transmitted by a flexible line containing an optical fiber is inserted through a limbel incision, preferably 1 mm or less, in the eye surface and then through a 1 mm or less anterior capulotomy into the lens nucleus. The optical fiber is then positioned within the crystalline lens.
Coherent radiation disintegrates the crystalline material into extremely small particles less than 0.1 mm in diameter. These nuclear particles and cortex can then be irrigated and aspirated from the capsular bag, which is left intact, except for the 1 mm anterior capsulotomy, via an aspiration sleeve which is formed about and extending along the optical fiber. At the same time irrigating liquid is supplied via an irrigation sleeve likewise formed about and extending along the optical fiber.
Since the particles produced by this ablation are so small, the device can be made to be extremely small and therefore, the incision likewise can be made much smaller than with other techniques such as ultrasonic. Utilizing an optical fiber further permits the energy to be more efficiently and effectively focused onto the lens to be removed.
Radiation in the range of 193 to 351 nm has proved to be satisfactory. In particular, 308 nm was found to be the most effective experimental wavelength. However, the invention is also effective at other wavelengths, for example, between 193 nm and 3000 nm.